DESCRIPTION: The objective of this research is to better understand the perception of complex acoustical stimuli. The auditory system has the property that incoming sounds are decomposed into different frequency channels. In contrast, our percepts are unified, depending on the integration of information across both frequency and time. The long- term objectives of the proposed research is to understand the integration of information across frequency. Of particular interest is the integration of level and temporal information, two features of broadband sounds encoded in frequency channels. This objective is addressed by comparing the result of psychophysical experiments and optimal statistical models of processing applied at the level of frequency channels. B jointly considering human performance predicted by optimal models, estimates of frequency selectivity for level and temporal tasks may be obtained. Then, the resulting models may be tested using increasingly complex tasks, tasks in which both level and temporal features of broadband stimuli are varied. To the degree that the sensitivity to changes in level and temporal features of broadband sounds are successfully modeled, comparisons with models derived for hearing impaired individuals can follow.